The practice, in the case of thermal coating processes, such as flame spraying or plasma spraying, of subjecting the surfaces to activation before coating is known from the prior art. Normally, this activation consists in roughening the surface by machining the surface with pressurized abrasive particles, in particular sharp-edged particles, such as white corundum. This step is also referred to as a jet machining process.
Jet machining processes of this kind have the disadvantage that the characteristics of the surfaces produced cannot be accurately reproduced and that the associated adhesive power of the coatings may be subject to large fluctuations, which is inappropriate for large-scale manufacture.